[smokeping-users] Re: Experience with FreeBSD 6.x and Smokeping

Vinny Abello vinny at tellurian.com
Thu Dec 7 17:58:56 MET 2006

Found my answers in the man files for icmp:

 icmplim         (integer) Bandwidth limit for ICMP replies in pack-
                     ets/second.  Used when icmplim_output is non-zero.
                     Defaults to 200.

 icmplim_output  (boolean) Enable/disable bandwidth limiting of ICMP
                     replies.  Defaults to true.

I'm going to increase this value to see if it helps my problem. I'm
still uncertain if that is in bytes or KB or something else. I'm leaning
towards KB as that would seem to be a sensible default. I'll write back
with my results for any others that this may benefit.

Vinny Abello wrote:
> Maybe these values are more of my problem:
> net.inet.icmp.icmplim: 200
> net.inet.icmp.icmplim_output: 1
> These are system defaults. I'm assuming the first limits the number of
> ICMP packets based on some interval which will probably need to be
> increased as things grow. I'm assuming the second value is just a
> boolean value to enable the kernel to use the limit defined in
> net.inet.icmp.icmplim. Anyone know for sure and have suggestions for the
> size of this parameter or if it is even possibly the cause of the problem?
> Vinny Abello wrote:
>> I adjusted these parameters... My maxfragpackets was actually at 2048.
>> Wouldn't the problem be if it's too small, not too large? The
>> maxfragsperpacket was already at 16.
>> Edinilson J. Santos wrote:
>>> You need to adjust some parameters in your sysctl.conf.
>>> Try something like (in sysctl.conf):
>>> net.inet.ip.maxfragpackets=40
>>> net.inet.ip.maxfragsperpacket=16
>>> and see what happens.
>>> Regards
>>> Edinilson
>>> ---------------------------------------------------------
>>> ATINET-Professional Web Hosting
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>>> ----- Original Message ----- 
>>> From: "Vinny Abello" <vinny at tellurian.com>
>>> To: <smokeping-users at list.ee.ethz.ch>
>>> Sent: Wednesday, December 06, 2006 4:11 PM
>>> Subject: [smokeping-users] Experience with FreeBSD 6.x and Smokeping
>>> Are there many people using FreeBSD 6.x and Smokeping?
>>> I asked this a while back but nobody seemed to have any input. Ever since 
>>> moving from FreeBSD 5.3 to 6.0 (currently 6.1) I have been seeing artificial 
>>> loss in smokeping that does not exist. It always shows up as two repeated 
>>> intervals of 19/20 packets received (light blue) and never at the same time 
>>> on any of the monitors. I think there is some sort of ICMP rate limiting or 
>>> something else going on in the kernel but I have never been able to locate 
>>> it. Users on the FreeBSD-Stable list didn't have any input either. You can 
>>> clearly see on all of my graphs at the precise time I upgraded from 5.3 to 
>>> 6.0 there is slight loss from that time forward. It makes the graphs that 
>>> are logged for long periods of time look bad (always light blue) instead of 
>>> mostly green which they should be (for my network anyway). I've done 
>>> numerous tests with other tools to verify there is no packet loss from the 
>>> same machine. I cannot reproduce the statistics I see with Smokeping using 
>>> anything else. I'm
>>>  hoping someone might have some input (other than use Linux). :)
>>> If you need any more information about my setup, just ask. Almost all probes 
>>> are Fping based and there are somewhere between 50 and 60 monitors setup. 
>>> The server is a Dell 2650 with dual P4 Xeon 2.8GHz CPU's. MP kernel is 
>>> enabled. I was toying with disabling MP to see if it was some sort of weird 
>>> problem with multiple CPU's.
>>> Any help or suggestions are appreciated! :)


Vinny Abello
Network Engineer
Server Management
vinny at tellurian.com
(973)300-9211 x 125
(973)940-6125 (Direct)
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